Cigarette wrapper with novel pattern

ABSTRACT

A wrapper for a smoking article has a base web and a plurality of crenellated bands, each having a diffusivity value in the range of 0 to about 0.2 cm/sec. The add-on material can be applied by gravure printing in a single pass in a chevron pattern such that an apex of the element is co-linear with substantially symmetrically spaced points on a trailing, outer edge of an adjacent chevron element. Testing elements may be simultaneously printed with the add-on material to monitor diffusivity and/or presence of add-on material.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a divisional of, and claims priority under 35 U.S.C. § 120 to, U.S. application Ser. No. 13/896,040, filed May 16, 2013, which claims priority from Provisional Application No. 61/647,918, filed May 16, 2012, the entire contents of each of which are incorporated herein by reference thereto.

WORKING ENVIRONMENT Ignition Propensity (“IP”)

A measure of the tendency of a smoking article to cause ignition when left placed upon a substrate is the Ignition Propensity value. An Ignition Propensity value, or IP value, of a smoking article should preferably be no greater than about 25%. More preferably, the IP value should be no greater than about 20%; and even more preferably no greater than about 10%.

Ignition Propensity or IP is a standard test conducted as set forth in ASTM E 2187-04, “Standard Test Method for Measuring the Ignition Strength of Smoking articles”, which is incorporated herein in its entirety by this reference thereto. Ignition propensity measures the probability that a smoking article, when smoldering and placed on a substrate, will generate sufficient heat to maintain smoldering of the tobacco rod. Low values for IP are desirable as such values correlate with a reduced likelihood that a smoldering smoking article, when inadvertently left unattended upon a substrate, will cause combustion in the substrate.

Self Extinguishment (“SE”)

Smoking articles exhibiting reduced IP values typically also tend to self-extinguish between puffs during smoldering, which is contrary to adult consumer expectations. Adult consumers do not like having to re-light a cigarette during their smoking experience.

A measure of the tendency for a smoking article to self-extinguish during free burn has been developed and is known as the Self-Extinguishment value. The Self-Extinguishment value or SE value has been found to be a useful indicia of the likelihood of a smoking article to self-extinguish between puffs during smoking. The Self-Extinguishment Average value for a smoking article should preferably be no greater than about 80% and/or the Self-Extinguishment at 0° value (0° indicating that the cigarette is smoldering in horizontal orientation) should be no greater than about 50%, and more preferably no greater than about 25%.

Self-Extinguishment or SE herein is a reference to smoldering characteristics of a smoking article under free burn conditions (away from any substrate). To evaluate SE, a laboratory test is conducted at a temperature of 23° C.±3° C. and relative humidity of 55%±5%, both of which should be monitored by a recording hygrothermograph. Exhaust hood(s) remove combustion products formed during testing. Prior to testing, smoking articles to be tested are conditioned at 55%±5% relative humidity and 23° C.±3° C. for at least 24 hours. To facilitate conditioning, the smoking articles are placed in glass beakers to assure free air access.

SE testing takes place within an enclosure or test box. A single port smoking machine or an electric lighter is used to ignite the smoking articles for the test. During testing, an apparatus or “angle holder” holds the smoking articles to be tested by holding an end at angles of 0° (horizontal), 45°, and/or 90° (vertical). Preferably, twenty (20) smoking articles are tested at each of the 0°, 45°, and 90° positions. If more than one apparatus is used, the apparatuses are preferably positioned such that the smoking articles face away from each other to avoid cross interference. If a smoking article goes out before the front line of the smoldering coal reaches the tipping paper, the outcome is scored as “self-extinguishment”; on the other hand, if the smoking article continues smoldering until the front line of the smoldering coal reaches the tipping paper, then the outcome is scored as “non-extinguishment”. Thus, for example, an SE value of 95% indicates that 95% of the smoking articles tested exhibited self-extinguishment under the free burn conditions; while an SE value of 20% indicates that only 20% of the smoking articles tested exhibited self-extinguishment under such free burn conditions.

The SE value may be referred to in terms of “Self-Extinguishment at 0° value”, “Self-Extinguishment at 45° value”, or “Self-Extinguishment at 90° value”, each of which refers to the value of SE at the specified tested angle. In addition, the SE value may be referred to in terms of “Self-Extinguishment Average value”, which refers to an average of the three angular positions: namely, an average of (i) the “Self-Extinguishment at 0° value” (level, or horizontal orientation), (ii) the “Self-Extinguishment at 45° value”, and (iii) the “Self-Extinguishment at 90° value” (vertical orientation). A reference to “Self-Extinguishment value” or “SE value” does not distinguish between SE at 0°, SE at 45°, SE at 90°, or SE average values and may refer to any one of them.

As noted above, it is desirable to achieve IP performance with a banded paper that meets and exceeds governmental requirements. As previously noted, achievement of a desired IP performance often adversely impacts the SE performance of the smoking article. Stated differently, while an IP performance of a smoking article may meet or exceed the governmental requirement (i.e., it has a 0% IP value), that level of IP performance typically results in a smoking article that will self-extinguish when the cigarette smolders away from any substrate (i.e., it has an SE value of 100%). Improvement of SE performance while maintaining requisite IP performance constitutes a highly desirable feature for cigarette wrappers and smoking articles constructed from them. Applicants have discovered arrangements of the bands on wrapper that provide such improved SE performance while maintaining the desired or requisite IP performance.

SUMMARY

In accordance with this disclosure, an improved cigarette wrapper and smoking article using that wrapper provides remarkably low IP and SE values, which values satisfy various governmental regulations and requirements for smoking articles. The improved wrapper exhibits circumferential banded regions of add-on material, where the add-on material is applied in a substantially sawtooth (crenellated) form in a single printing application, wherein at least one edge portion comprises crenels and merlons (crenallated). In a first preferred embodiment, both the leading and trailing edge portions of each band are crenallated, and in a second preferred embodiment only one of the edge portions (preferably the leading edge portion) is crenallated. The bands of either embodiment are longitudinally spaced from one another by a distance of preferably about 20 to about 22 mm.

The crenelated bands are preferably applied to a base web using an aqueous starch solution containing an anti-wrinkling agent and calcium carbonate. Preferably, the anti-wrinkling agent comprises propylene glycol. Particularly preferred composition of the aqueous starch solution are explained more fully below. Nevertheless, when dried, the add-on material in the bands exhibits a diffusivity in the range of 0 to about 0.2 cm/sec, and preferably in the range of 0 to about 0.1 cm/sec.

Preferably, the add-on material is applied to the base web in a single step, gravure printing operation, which operation includes maintenance of the add-on material at temperatures sufficient to avoid degradation of the aqueous starch solution. Single pass operations with measures to abate wrinkling of the base web have been avoided to present difficult alignment and registration issues encountered in high speed multi-pass operations. Practice of the teachings herein provides a wrapper having enhanced consistency and more predictable ignition propensity (IP) and SE performances.

Preferably, the diffusivity value throughout the banded regions is in the range of about 0.0 to 0.2 cm/sec, more preferably, less than 0.1 cm/sec.

Preferably, the printed pattern on the base web includes one or more longitudinally extending lanes of spaced apart rows of bands of a nominal add-on rate, together with one or more lanes of test marks adjacent to the lane(s) of bands. Preferably, the test marks are applied to the base web at the same add-on rate as for the bands and may comprise a plurality of spaced-apart solid bands of add-on material or other geometric form of sufficient size and/or geometry to facilitate measurement of diffusivity for purposes of quality control. As spaced-apart solid bands, the test marks also can be used to optically inspect the base web during printing operations to confirm presence of desired print patterns along the base web during its conversion.

BRIEF DESCRIPTION OF THE DRAWINGS

Many objects and advantages of the present disclosure will be apparent to those skilled in the art when this specification is read in conjunction with the accompanying drawings, wherein like reference numerals are applied to like bands and wherein:

FIG. 1 is a perspective view of a smoking article according to the disclosure, where the bands are shown in solid lines for illustrative purposes.

FIG. 2 is a plan view of a portion of a base web with a band applied thereto.

FIG. 3 is a plan view with dimensional details of a band according to a first embodiment as shown in FIG. 2.

FIG. 4 is a plan view with dimensional details of a band according to a second embodiment.

FIG. 5 is a process flow diagram of a process for making and applying an aqueous starch solution to a base web.

FIG. 6 is a schematic view of a gravure printing system.

FIG. 7 is schematic perspective view of a gravure roller according to the disclosure.

FIG. 8 is a plan view of a base web with representation in outline of areas where bands applied thereto.

FIG. 9 is a reduced scale view of a base web which includes primary lanes comprising spaced-apart transverse rows of printed bands and supplementary lanes comprising spaced-apart transverse test marks in the form of solid banded regions.

DETAILED DESCRIPTION

Referring to FIG. 1, in a preferred embodiment, a smoking article 120 (e.g., a cigarette) preferably comprises a tobacco rod 122 and optionally a filter 132 attached to the tobacco rod 122 with a tipping paper 193. The tobacco rod 122 comprises a column of smokeable material (e.g., tobacco cut filler) and a wrapper 122′ disposed about the column of smokeable material.

The wrapper 122′ of the smoking article 120 comprises a base web 140 (see FIGS. 2 and 9) having a nominal permeability and a plurality of banded regions 126 applied thereto with sufficient add-on material such that the wrapper has a permeability at the banded region 126 less than the nominal permeability of the base web. In a first embodiment, a leading edge 500 and a trailing edge 502 of each banded region 126 is crenellated. In a second embodiment, only one of the leading and trailing edge portions of the banded region is crenellated.

Referring to FIG. 2, the banded region 126 may have a leading edge 500 in which the crenels 504 are disposed between merlons 506. In this first embodiment, the merlons 506 have a dimension in the transverse direction of the base web 140 which is substantially the same as the dimension in the transverse direction of the crenels 504. As depicted, the merlons 506 and associated crenels 504 are preferably rectangular. If desired, however, the merlons 506 and crenels 504 may have other geometric shapes including, without limitation, quadrilaterals, trapezoids, triangles, hexagons, and other regular or irregular geometric configurations. The distance between the top of a merlon 506 and the bottom of an adjacent crenel 504 may lie in the range of about 2 mm to about 5 mm, and preferably may be about 3 mm. At the trailing edge 502 of the banded region 126, a similarly crenellated arrangement may also be provided.

Preferably, an integral number of pairs of merlons 506 and crenels 504 corresponds to the nominal circumference of smoking article with accommodation for overlapping edges along the seam of the cigarette 120. For example for a tobacco rod of an 24.8 mm circumference, the transverse dimensions of a pair of a merlon 506 and a crenal 504 may be established at about 8.4 mm, such that 4 pairs will be established about the circumference of the tobacco rod and the alternating crenel/merlon pattern remains established even at the seam.

Preferably, the longitudinal dimension or height y of the merlons 506 (or the corresponding depth of the crenels 504) is preferably less than the longitudinal extent x of the solid, central, circumferential portion 508 of the band 126. In this embodiment, the trailing edge 502 is preferably provided with crenals 514 and merlons 516 that are arranged similarly. Preferably, where a merlon 506 appears along the leading edge 500, a crenal appears on the trailing edge 502 and visa versa.

Referring now to FIG. 1, preferably, the bands of the first embodiment have an overall width “w” measured in the longitudinal direction of the wrapper, which width preferably lies in the range of about 7 to about 14 mm, more preferably in the range of about 8 to about 12 mm, even more preferably about 10 mm. Preferably, the crenellated band 126 (FIG. 2) includes a central solid circumferential region 508 (of about 4 mm width “x”) and further includes merlons 506, 516 extending longitudinally a distance “y” of about 3 mm from opposite sides of the solid banded region 508 in alternating relationship with crenels preferably of the same longitudinal extent. In the first embodiment, preferably each merlon 506, 516 and crenel 504, 514 have a substantially equal circumferential or transverse dimension of about 4.1 mm. Preferably band spacing (shown as “s” in FIG. 1) of the first embodiment is in the range of about 20 to 22 mm.

There is a host of alternate geometries that might be attempted in a design of a crenellated band, including changing transverse and longitudinal dimensions of the geometric components (the solid central region 508, the merlons 506, 516 and the crenels 504, 514), or changing their relative size (equal verses unequal) or changing the geometric components from one edge portion 500 to the next 502 or from band 126 to the next. The geometry shown and described with reference to FIG. 3 (and also those with reference to FIG. 4) were used in testing and were found to produce surprisingly good IP and SE values, which results are set forth in the examples near the conclusion of these teachings.

Referring now to FIG. 4, in a second embodiment, the banded regions 126′ have an overall width measured in the longitudinal direction of the wrapper, which width preferably lies in the range of about 5 to about 11 mm, more preferably in the range of about 6 to about 8 mm, more preferably about 7 mm, wherein of that 7 mm, 4 mm is a central solid circumferential region 508′ of about 4 mm width, with merlons 506′ extending longitudinally about 3 mm from the central region 508′, but only along one of the leading edge 500 (as shown in FIG. 4) or the trailing edge (not shown). In the second embodiment, preferably each merlon and crenel have substantially equal circumferential or transverse dimensions of about 3.1 mm. Preferably band spacing of the second embodiment is in the range of about 20 to 22 mm.

Preferably, each band 126 is formed of an add-on solution which is aqueous and applied in a single pass, gravure printing operation, which operation includes maintenance of the add-on material at temperatures sufficient to avoid degradation of the aqueous starch solution (see FIG. 5). Single pass operations with measure to abate wrinkling of the base web have been found to promote precise printing execution and avoid misalignment or mis-registration issues during high speed printing multi-pass operations. The preferred measures to abate wrinkling include provision of an anti-wrinkling agent in an aqueous starch add-on solution, which preferably also includes calcium carbonate. Another technique to further abate wrinkling (and creasing of cigarette wrapper) is to use a chevron printing pattern for application of the rows 131 of bands 126 instead of straight lines without angularity, such as described in the teachings which follow with reference to FIGS. 6-8.

Preferably, the material is applied at a rate sufficient to achieve a diffusivity value of about 0 to about 0.2 cm/sec, preferably 0 to about 0.1 cm/sec.

Referring now to FIG. 9, preferably, the printed pattern 806 of the base web 140 includes one or more longitudinally extending lanes 810, 810′ of spaced apart rows131, 131′ of bands 126 of a nominal add-on rate together with one or more supplemental lanes 812, 812′, 812″ of test marks 814, 814′, 814″ adjacent to the lane(s) 810, 810′ of bands 126. Preferably, the test marks 814 are applied to the base web 140 at essentially the same add-on rate (i.e., same solution, same engraving depth/cell dimensions) as for the bands 126 and may comprise a plurality of spaced-apart solid bands of add-on material or other geometric form of sufficient size and/or geometry to facilitate measurement of diffusivity for purposes of quality control.

In a preferred embodiment, the clamp mechanism of the diffusivity tester encloses a rectangular area of base web of approximately 4 mm by 15 mm. Accordingly, the test marks 810, 810′ are sized greater than the enclosed area of the clamp. In this embodiment, the reference marks 810, 810′ are sized approximately 5-6 mm wide and extend transversely by at least several inches. The latter could be shortened.

The reference or test marks 810, 810′ are configured to make possible testing for diffusivity, whereas the bands 126 themselves are not so configured. The ability to measure the diffusivity values in regions bearing the applied add-on material reduces the need to make test cigarettes and to conduct ignition propensity tests of smoldering cigarettes. Instead, the diffusivity of the test marks 810, 810′ is measured to confirm or deny by correlation that the bands 126 in adjacent portions of the base web are at the desired level of diffusivity and therefore possess the desired level of IP performance. Being able to monitor diffusivity values avoids the waste and cost associated with preparing cigarettes and actually conducting ignition propensity tests. As spaced-apart solid bands, the test marks can also be used to optically inspect the base web during printing operations to confirm presence of desired print patterns along the base web during its conversion. Suitable optical inspection techniques include those described in U.S. Pat. No. 6,198,537, which is incorporated herein by reference in its entirety. Other inspection techniques could be employed, including those which utilize wavelengths other than visible.

All of the above-mentioned teachings and the further details which follow contribute to a wrapper 123 which can provide enhanced and more balanced IP performance and SE performance in smoking articles constructed therefrom. Additionally, with the abatement of wrinkling and single-pass operation, the bands 126 can be precisely and more uniformly printed at commercially acceptable printing speeds, which can be monitored during their construction to assure acceptable levels of quality control. Further details of the preferred embodiments are provided in the description which follows.

Definitions

As used herein, the phrase “leading edge” refers to the edge 500 (see FIG. 1) of a band 126 that is closest to an approaching coal during smoldering of a smoking article 120 whose wrapper 123 contains the bands 126, while the phrase “trailing edge” refers to the edge 502 of a band 126 that is farthest from an approaching coal during smoldering of a smoking article 120 whose wrapper 123 contains the band 126.

With reference to FIG. 1, for purposes of this disclosure, “band spacing” or refers to the distance “s” in FIG. 1 between the trailing edge 502 of a band 126 and the nearest leading edge 500 of a band 126′.

An “anti-wrinkling agent” is a material which abates the tendency of an aqueous starch solution to shrink a base web upon its application and drying. A suitable anti-wrinkling agent may be selected from the group consisting of 1,2 propylene glycol, propylene glycol, and glycerin. Other anti-wrinkling agents can be used in addition to, or in lieu of the preferred materials. For example, other suitable anti-wrinkling agents include polyols, including without limitation, glycerol, polyethylene glycol, glucose, sucrose, isomalt, maltilol, sorbitol, xylitol, and other agents exhibiting comparable functionalities.

For purposes of this disclosure, “layer” refers to a unitary quantity of add-on material applied to a base web from which a wrapper is fabricated. A band 126 may be fashioned from one or more layers that may be superimposed on one another; however experience with multi-pass applications has shown a tendency of the base web 140 to wrinkle upon application of an aqueous solution, which confounds proper alignment and registration between applications of the band pattern, which caused consistency and predictability in a wrapper's IP performance to suffer. Accordingly, it is preferred to apply bands 126 in a single-pass gravure operation, and further preferred to include with the single-pass operations measures which abate wrinkling of the base web 140.

For purposes of this disclosure, “longitudinal” refers to the direction along the length of a tobacco rod (e.g., along the axis 137 in FIG. 1), or along the length of a base web 140 (e.g., arrow 141 in FIG. 2) used in the preparation of wrapper that, in turn, may be used to fabricate a tobacco rod, or in the so-called machine-direction of a printing press, i.e., the direction through which a base web is drawn through a print station(s).

For purposes of this disclosure, “transverse” refers to the direction circumferentially around a tobacco rod 122 (see FIG. 1), or transversely of a base web 140 (e.g., arrow 144 in FIG. 2) which corresponds with the so-called cross-machine direction of a printing press.

For purposes of this disclosure and with reference to “w” in FIG. 1, the “width” of an individual band 126 or banded region extends in a longitudinal direction (e.g., in the direction of axis 137 in FIG. 1 and the arrow 141 in FIG. 2).

In this specification, the unit of measurement for basis weight, gram(s) per square meter, is abbreviated as “gsm”.

When the phrase “weight percent” is used herein with respect to the starch component of a starch solution, the “weight percent” is the ratio of the weight of the starch to the total weight of the starch solution. Unless noted otherwise, when the phrase “weight percent” is used herein with respect to any component other than the starch component of a starch solution, the “weight percent” is the ratio of the weight of that other component to the weight of the starch component.

For gravure printing applications, the phrase “single pass” as used in the specification is intended to mean printing using a single cylinder. For other application techniques, the phrase “single pass” is intended to mean a process where the entire band or pattern is applied at one time.

When reference is made to percentages in this specification, it is intended that those percentages are based on weight, i.e., weight percentages.

The phrases “self-extinguish under free-burn conditions” or “self-extinguishment” as used herein, refer to the extinguishment of a smoldering cigarette without puffing, when such cigarette is subjected or exposed to free-burn conditions.

When the word “about” is used in this specification in connection with a numerical value, it is intended that the associated numerical value include a tolerance of ±10% around the stated numerical value.

The terms and phrases used herein are not to be interpreted with mathematical or geometric precision, rather geometric terminology is to be interpreted as meaning approximating or similar to the geometric terms and concepts. Terms such as “generally” and “substantially” are intended to encompass both precise meanings of the associated terms and concepts as well as to provide reasonable latitude which is consistent with form, function, and/or meaning.

Smoking Article with Improved Wrapper

Referring again to FIG. 1, a smoking article 120, such as a cigarette, preferably includes a tobacco rod 122 and a filter 132 attached to the tobacco rod 122 with tipping paper 193. Preferably, the tobacco rod 122 comprises a column of shredded tobacco (“cut filler”) and a wrapper 123 disposed about the column of tobacco, which wrapper 123 is constructed in accordance with teachings which follow. The tobacco rod 122 has a lightable or lit end 124 and a tipped end 132 (which in the case of non-filter cigarettes, is referenced as the mouth end 132 of the cigarette 120). Cut filler tobacco is an industry-standard designation. Further, the tobacco rod 122 typically has a generally circular cross section, although other oval cross section and other shapes are within the scope of this disclosure. The wrapper is sealed along a longitudinal seam to form the tobacco rod 122.

The tobacco rod has a nominal length “L” measured from the edge 130 of the tipping paper 193 to the lit end 124 of the tobacco rod along a longitudinal axis 137 of smoking article. By way of example, that nominal length may lie in the range of about 50 to about 100 mm.

As shown in FIG. 2, the wrapper 123 is constructed from a base web 140 that may be made from flax, wood pulp, cellulose fiber, or the like, and may have a plurality of crenellated (or “sawtooth”) bands 126 applied to one or both sides of the base web 140. Preferably, the band 126 is applied to the inside of the wrapper 123 in the sense of how the wrapper 123 surrounds a column of tobacco in the tobacco rod 122 (shown in FIG. 1).

Preferably, the transverse dimensions of the wrapper 123 are selected based on the diameter of the finished smoking article (about 5 to about 10 mm) and allowing for overlapping material at a longitudinal seam of about 1 to about 2 mm. For example, allowing for about 2 mm overlapping seams, the wrapper-paper cross-web dimension may be about 27 mm for a smoking article having a circumference of about 24.8 mm.

The wrapper includes a base web which typically is permeable to air. Permeability of wrapper is typically identified in CORESTA units. A CORESTA unit measures paper permeability in terms of volumetric flow rate (i.e., cm³/sec) per unit area (i.e., cm²) per unit pressure drop (i.e., cm of water). The base web of conventional wrapper also has well-known basis weights, measured in grams per square meter, abbreviated as “gsm”. The permeability and basis weight for base web of typical smoking article papers commonly used in the industry are set out in the table below:

Permeability, CORESTA units Basis Weight, gsm 24 25 33 24-26 46 24-26 60 26-28

For purposes of this description, the base web of a preferred wrapper has a permeability of at least about 20 CORESTA units. Most preferably, the wrapper has a permeability greater than about 30 CORESTA, such as common base webs having nominal permeabilities of about 33 and about 46 CORESTA with a basis weight of about 25 gsm. For some applications, the base web may have a permeability of greater than about 60 CORESTA, or greater than about 80 CORESTA, or even higher permeability values, with a basis weight of about 26 gsm or greater.

Each layer of add-on material may be substantially continuous, may have a uniform or variable thickness, and/or may have a smooth or rough surface.

Techniques other than gravure printing may be used to produce the desired bands 126, such a xerographic printing, digital printing, coating or spraying using a template, or any other suitable technique or including a separate step for establishing material-free regions. However, single-pass, gravure printing techniques are preferred.

Diffusivity

When using the preferred add-on solutions, base webs and application techniques of the teachings which follow, a printing solution, upon its application to a base web and drying, forms an air-occlusive film on the base web that is effective to locally reduce diffusivity values from a diffusivity level of approximately 2 cm/sec or greater (for the base web in its original condition) to a value in the range of 0.0 to about 0.2 cm/sec, more preferably less than approximately 0.1 cm/sec, as measured by a Sodim CO₂ Diffusivity Tester (purchased from Sodim SAS of France). To measure the diffusivity of a piece of paper using a Diffusivity Tester, the paper is positioned within a clamping head so that the paper separates two vertically arranged chambers. The upper chamber contains a carrier gas, such as nitrogen, while the lower chamber contains a marker gas, such as carbon dioxide. As there is no pressure difference between the two chambers, any migration of gases is due to differences in concentrations of the gases, and there is no permeability effect, which occurs when a pressure difference is maintained between two surfaces of the paper. After a predetermined period of time (e.g., for about 25 seconds), the concentration of carbon dioxide within the nitrogen stream of the upper chamber is measured in an analyzer. A computer then converts the detected level of concentration into a measure of diffusivity.

Preparation of Add-On Material

As described in U.S. Patent Application Publication No. 2008/0295854 filed May 23, 2008, the entire content of which is incorporated by reference thereto, preferably, a film-forming composition may be used to form the bands 126. The film-forming composition comprises water and a high concentration of an occluding agent, e.g., about 14% to about 50% by weight of the water plus the occluding agent. The film-forming compound can include one or more occluding agents such as starch, alginate, cellulose, or gum and may further include calcium carbonate as a filler. Further, the film-forming composition preferably includes an anti-wrinkling agent. Where starch is the film-forming compound, a concentration of about 16% to about 26% may be particularly advantageous, and a concentration of about 21% is presently most preferred.

To improve the ignition propensity characteristics of a smoking article fashioned from the wrapper, the pattern is preferably applied with a printing solution containing an oxidized starch and formed by a process as described herein. Preferred printing characteristics and film-forming characteristics of the add-on material may be achieved using an aqueous oxidized starch solution having a viscosity ranging from about 40 centiPoises (cP) to about 80 cP as measured using a Brookfield RVDV-2 viscometer with a #1 spindle at 20 rotations per minute (rpm) as measured at 120° F., more preferably in the range of about 40 cP to about 60 cP. At the press or at time of printing, the viscosity is adjusted by an addition of hot water and/or heat to achieve a preferred final, print solution having a viscosity of about 16.5 to about 19.5 seconds, as measured by a Zahn #2 cup at 120° F., more preferably about 17 seconds to about 19 seconds. Starch employed for the printing solution preferably may be initially mixed with water to form an aqueous starch mixture having a solids content of about 29% to about 34% (by weight), more preferably about 30% to about 33% (by weight). While various starches may be used, for purposes of this invention it is preferred, without limitation, to use an oxidized starch. Preferred oxidized starches include an oxidized tapioca starch, such as FloMax® 8 available from National Starch, LLC (now Ingredion). The type (e.g. tapioca) and treatment (e.g. oxidation) provides starch components (e.g. amylose and amylopectin) that are in the preferred molecular weight range.

Preferably, the printing solution also includes 1, 2-propylene glycol, in amounts sufficient to abate the tendency of the base web to wrinkle in the course of applying and drying an aqueous starch solution during printing (the “anti-wrinkling” effect of propylene glycol). It is presently understood that this effect is achieved at inclusion levels which result in there being, in the final wrapper, a presence of propylene glycol in the bands at a basis weight level of about 0.2 to 0.5 grams per square meter or more. Further teachings regarding inclusion levels of propylene glycol and other “anti-wrinkling” agents are set forth in commonly assigned, U.S. Patent Application Ser. No. 61/064,438, “Patterned Wrapper with an Anti-Wrinkling Agent,” filed Mar. 5, 2008, the content of which is incorporated herein by this reference thereto.

A presently preferred solution may comprise at the press (all percentages here being based on the total solution weight): starch—in an amount of about 18 to about 23 wt % (weight-percent), more preferably about 20 to about 22 wt %, and even more preferably about 21 wt % of the total solution weight; propylene glycol—in an amount ranging from about 7 to about 10 wt %, more preferably about 7 to about 9 wt %, and even more preferably about 8 wt % of the total solution weight; calcium carbonate—in an amount in the range of about 9 to about 13 wt %, more preferably about 10 to about 12 wt %, and even more preferably about 11 wt % of the total solution weight; with water essentially comprising the remainder (in an amount ranging from about 55 to about 65 wt %, more preferably about 60 wt %).

It has been further discovered that at preferred inclusion levels, and upon addition of propylene glycol at or near the conclusion of cooking of the aqueous oxidized starch solution, the propylene glycol has additional beneficial effects. Upon its inclusion in a cooked aqueous starch solution, it abates the tendency of the starch components to retrograde or gel, so as to act as a stabilizing agent. It also provides anti-microbial effects in the resulting printing solution. Both of these effects enhance the shelf life of the printing solution. The enhanced shelf life of the printing solution makes it possible to prepare the solution remotely from where printing operations are to occur and to ship the solution. As will be further explained in the teachings which follow, the operational shelf life of the printing solution is further enhanced by maintaining the printing solution in the range of 120 to 150° F., more preferably about 120° F. to about 140° F., during transit and/or at the time of printing. Furthermore, inclusion of propylene glycol in the process as taught herein also has the effect of reducing the printing solution's viscosity to levels, which further promotes its printability.

Preferably, a conventional filler material, such as calcium carbonate, may be included in the printing solution, as desired, to lighten the printed material to make it less visible on the wrapper and to improve self extinguishment performance of the finished smoking article. Preferably, if included, the calcium carbonate is added to the printing solution just before printing. The calcium carbonate may also help abate wrinkling of the wrapper by reducing the water content in the applied solution. Preferably, the printing solution has a pH in the range of about 4 to about 8, more preferably about 7 to about 8 after calcium carbonate has been added thereto.

Furthermore, the predetermined pattern of printing solution is typically applied to a base web having a permeability in the range of about 10 to about 80 CORESTA units. Preferably, the printing solution forms a film on the base web, when dry, that is effective to locally reduce diffusivity values in the range of 0 to about 0.20 centimeters per second (cm/sec) as measured by a Sodim CO₂ Diffusivity Tester (available from Sodim SAS of France, more preferably diffusivity values in the range of 0 to about 0.10 cm/sec.

Various balances or trade-offs need to be made in selection of starch parameters for use in applying films to wrapper. For example, while high molecular weight starch may give rise to effective diffusivity reduction, such high molecular weight starches are of lower solubility, and consequently, must be used in lower concentrations, resulting in a printing solution and with very high water content, which elevates drying requirements and exacerbates the wrinkling of the base web.

In the preferred embodiment, as shown in FIG. 3, the printing solution is prepared by adding water 200 and adding oxidized starch 205 to a container in a batch process. The preferred embodiment provides a batch process. In the batch process, the water and an oxidized starch are mixed (step 210) at about 75° F. at low speeds of about 15 rotations per minute (rpm) to disperse the starch granulars in water and form an aqueous oxidized starch mixture having a pH in the range of about 4 to about 5.5. In the preferred embodiment, the water may be heated to about 75° F. or more before adding (step 205) the oxidized starch thereto. Upon mixing (step 210), the oxidized starch mixture is then heated (step 220) to a temperature in the range of at least about 180° F. to at least about 200° F., more preferably about 195° F. Preferably, the temperature is raised over a preferred time interval of about 60 to about 90 minutes, preferably with agitation so as to assure uniformity. Also preferably, the temperature of the heated oxidized starch mixture is then “cooked” by maintaining (step 230) the solution at the aforementioned selected temperature in the range of about 180° F. to about 200° F., preferably at about 195° F. while mixing for at least about 30 minutes, more preferably at least about 45 minutes. During the heating and maintaining steps, the starch granules (detectable under a microscope) are believed to absorb water, swell, rupture, and release amylose and/or amylopectin into the solution.

After the heating (step 220) and the maintaining (step 230) the temperature of the aqueous oxidized starch solution, the process preferably also includes adding (step 250) propylene glycol to the aqueous oxidized starch solution and mixing (step 260) while holding the temperature substantially constant either at aforementioned, selected temperature, or more preferably, at or about 180° F. If, when adding propylene glycol, it is at room temperature, the temperature of the solution may drop from the aforementioned 195° F. to a temperature of about 180° F. Once the propylene glycol is added (step 250), the aqueous oxidized starch solution is mixed for at least about 30 minutes to thoroughly disperse the propylene glycol throughout the aqueous oxidized starch solution.

Preferably, the aqueous oxidized starch solution is continuously mixed during the heating (step 220), the maintaining (step 230), and after the adding (step 250). Preferably, the propylene glycol is maintained at room temperature or higher before its addition to the aqueous oxidized starch solution. Moreover, the propylene glycol is preferably added as quickly as possible to the aqueous oxidized starch solution. In a batch process, for example, the aqueous oxidized starch mixture can be mixed using low speed, low shear mixing of about 15 rpm in a 1000 gallon tank during the heating (step 220), during the maintaining (step 230), and after the adding propylene glycol to the aqueous oxidized starch solution (step 250). Preferably, the mixing (step 260) is conducted while the solution is at an elevated temperature, preferably at about 180° F. or above.

In an alternative embodiment, the heating (step 220) can be accomplished by use of a jet cooker, which produces cooked starch on a substantially continuous basis “on demand”, where liquid heated to at least about 180° C. is jetted against an impaction surface to break-up granular structures of the starch in the liquid.

Not wishing to be bound by theory, it is believed that by maintaining the temperature of the aqueous oxidized starch mixture at or above about 195° F., the starch granules are caused to swell, rupture, and release amylose and/or amylopectin therefrom. By adding propylene glycol thereafter, it is believed that the propylene glycol substantially abates recombination thereof so that the film forming capability of the starch printing solution is preserved for an extended period of time. Moreover, the propylene glycol stays in solution with the starch to provide a substantially homogenous mixture having a low viscosity of less than about 100 cP, more preferably less than about 60 cP, more preferably about 40 cP to about 60 cP when measured using a Brookfield RVDV-2 viscometer with a #1 spindle at 20 rpm at 120° F.

Moreover, it is believed that the addition of propylene glycol to the aqueous oxidized starch solution provides stability and anti-microbial effects, and therefore, improved shelf-life to the printing solution. These effects are evidenced by the solution pH, which does not change (i.e., is substantially constant) for several days after the printing solution has been prepared.

After addition of propylene glycol (step 250) and the mixing (step 260), the printing solution may be cooled (step 240) to a temperature ranging from about 120° F. to about 140° F. Preferably, the printing solution is maintained at a temperature at about or greater than about 120° F. to avoid agglomeration and viscosity increase. It has been found that as the solution temperature drops below about 100° F., retrogradation accelerates resulting in undesired gelling of the solution. Once the gelling effect begins, the retrograded condition of the solution is irreversible.

At a temperature of about 120° F., the printing solution prior to initiation of printing operations preferably has a viscosity of about 40 cP to about 60 cP as measured using a Brookfield RVDV-2 viscometer with a #1 spindle at 20 rpm at 120° F. Also preferably, at a temperature of about 120° F. the printing solution has a pH of about 4 to about 5. At the press, just prior to initiation of printing operations either an addition of hot water or an increase in temperature (not higher than 150° F.) or both may be used to achieve a desired, final printing viscosity (in the range of about 16.5 to 19.5 sec, more preferably about 17 to 19 sec).

In one embodiment, the printing solution may then be stored in drums/totes and at a temperature of about 120° to about 140° F. until use at the time of printing. The drums/totes can be transported using an insulated blanket or heated truck, as needed, while maintaining the drums at a temperature of at least about 120° F. The drums/totes can also be stored under heated conditions. In the preferred embodiment, the printing solution may also be continuously agitated at low speed during storage. Preferably, the printing solution is used within 72 hours of production. The aforementioned maintenance of temperature, together with the addition of the propylene glycol provide stability to the solution such that a shelf-life of at least 2 or 3 days or longer is achievable.

In the preferred embodiment, the process may also preferably include adding (step 270) calcium carbonate to the printing solution. In the preferred embodiment, about 300 pounds of the printing solution can be mixed with about 40 pounds of water and about 40 pounds of calcium carbonate while mixing for about 15 to about 25 minutes. Preferably, the mixture is mixed using a Neptune impeller at low speed to suspend the calcium carbonate (or chalk) in the mixture, avoid foaming, and form a printing solution. The calcium carbonate is preferably added just before printing so that the calcium carbonate does not settle out of solution.

At the converter/printer, the printing solution can then be pumped to a run drum of a printing press. Preferably, the final printing solution (after addition of water and calcium carbonate) has a pH of about 7 to about 8 and a viscosity of about 20 cP as measured using a Brookfield RVDV-2 viscometer with a #1 spindle at 20 rpm at 120° F.

At the press, the process also includes providing a base web of wrapper (step 280) and applying the printing solution to the base web to form a cigarette wrapper (step 290).

In the preferred embodiment, the printing solution allows for higher starch loading to the base web, uses less water, and the propylene glycol has a greater anti-wrinkling effect due to a higher concentration of propylene glycol with respect to the water content. These features synergistically substantially reduce wrinkling of the base web and reduce the viscosity of the printing solution so as to enhance printability. For example, after application to a 33 CORESTA base web for a 6.8 mm wide solid band, with a 27 mm band period, about 0.9 grams per square meter (g/m²) starch, about 0.4 g/m² propylene glycol and about 0.4 g/m² calcium carbonate is deposited on the base web.

The following examples are given to illustrate embodiments of the process described herein and should not be construed to limit the scope of such embodiments.

EXAMPLE 1

Oxidized starch and water are mixed at about 75° F. and heated to about 195° F. for about 45 minutes with low agitation (low shear mixing) to form a mixture. The solution is removed from heat and propylene glycol is added thereto while mixing for about 30 more minutes while maintaining the solution at a temperature of at least about 180° F. The solution is cooled to a temperature of about 140° F. while mixing. The solution is then packed and the temperature of the solution is maintained at a temperature ranging from about 120° F. to about 140° F. and transported to a location of a press.

The solution contains about 31% (by weight) starch, about 10% (by weight) propylene glycol and about 59% (by weight) water. At the press or printing operation, about 300 pounds of the solution is then mixed with 40 pounds hot water and about 40 pounds calcium carbonate to form a printing solution having about 21% (by weight) starch, about 8% (by weight) propylene glycol, about 60% (by weight) water and about 11% (by weight) calcium carbonate to form a final, preferred printing solution.

The solution exhibited desired printability and film-forming characteristics.

EXAMPLE 2

About 51 pounds water heated to a temperature of about 70° F. to about 80° F. is mixed with about 31 pounds of starch powder, such as FloMax® 8 available from National Starch, LLC (now Ingredion). The water and starch powder are further mixed while heating for about 45 minutes to a temperature of about 200° F. to form an aqueous oxidized starch solution. About 10 pounds of either condensed steam or additional water heated to about 200° F. is added to the aqueous oxidized starch solution. The aqueous oxidized starch solution is tested using an oven bake method and has a solids content of about 31%. The viscosity is tested using a Brookfield RVDV-2 viscometer with a #1 spindle at 20 rpm at 120° F., and the aqueous oxidized starch solution is found to have a viscosity of about 50 cP. The aqueous oxidized starch solution has a pH of about 4 to about 5.

About 8 pounds of propylene glycol are then added to the aqueous oxidized starch solution and is mixed for about 30 minutes at a temperature ranging from about 180° F. to about 200° F. The printing solution is then cooled to a temperature of about 130° F. The viscosity is tested again using a Brookfield RVDV-2 viscometer with a #1 spindle at 20 rpm at 120° F., and the printing solution is found to have a viscosity of about 45 cP. Such evidences the favorable effect of the propylene glycol to reduce viscosity. The printing solution is kept under substantially constant agitation, the intensity of which is dependent upon tank size, dimensions and agitator type. Calcium carbonate is added while mixing to suspend the calcium carbonate and form a printing solution which is maintained at a temperature of about 120° F. to about 130° F. The printing solution contains about 54.5 pounds of water, about 24.5 pounds of pounds starch, about 10.5 pounds calcium carbonate, and about 10.5 pounds propylene glycol; and has a viscosity of about 17.5 sec to about 18.5 sec as measured by a Zahn #2 cup at 120° F.

As an alternative, turbidity of the aqueous oxidized starch and propylene glycol solution can also be measured to identify changes in the aqueous oxidized starch and propylene glycol solution before viscosity changes are noticed using viscosity measurements. Turbidity measures the amount of light transmitted through a given quantity of material, and can thus be used as a quality control tool to determine if the aqueous oxidized starch and propylene glycol solution should be used or discarded prior to mixing with calcium carbonate. Thus, the turbidity measurement can be used to determine the film-forming capability of the aqueous oxidized starch and propylene glycol solution.

In practicing the preferred embodiment of this invention, the step of maintaining the solution temperature in the range of about 120° to about 150° F. provides numerous advantages including, without limitation, permitting high starch content to be attained and maintained in the aqueous solution and lowering the aqueous solution's viscosity. Accordingly, through use of the temperature maintenance step until the printing step, a desired printing solution is achieved, which solution is suitable for a single pass application to a base web.

When propylene glycol is applied as an anti-wrinkling agent in accordance with this specification, the propylene glycol also counteracts the tendency of certain microorganisms to thrive in a starch solution at a temperature in the range of about 120° to about 150° F.

The film-forming composition may be applied to the base web of the wrapper 140 using gravure printing, digital printing, coating or spraying using a template, or any other suitable technique. Because of the intricate dimensions of the material-free regions of the various embodiments, a single-pass gravure printing operation is preferred. However, if desired, the bands 126 of add-on material can be formed by printing multiple, successive layers, e.g., two or more successive layers registered or aligned with one another.

For single-pass gravure printing operations, an aqueous starch solution of an embodiment comprises at least 25% starch by weight; between about 20% and about 35% anti-wrinkling agent (preferably propylene glycol), and between about 30% and about 80% chalk (preferably a fine calcium carbonate) percentages here being based on percent of starch weight). Preferably the aqueous starch solution is applied at the press at a temperature between about 120 to 140° F. and is preferably prepared and applied in accordance with those and other teachings of the commonly owned, U.S. patent application Ser. No. 13/324747, filed Dec. 13, 2011, the entirety of which is incorporated herein by reference. For multi-pass operations, a preferred aqueous solution may comprise approximately 16% starch, 6% chalk or calcium carbonate, and 6% 1,2 propylene glycol (weight percents of solution).

A preferred solution may comprise at the press (all percentages here being based on the total solution weight): starch—in an amount of about 18 to about 23 wt % (weight percent), more preferably about 20 to about 22 wt %, and even more preferably about 21 wt % of the total solution weight; propylene glycol—in an amount ranging from about 7 to about 10 wt %, more preferably about 7 to about 9 wt %, and even more preferably about 8 wt % of the total solution weight; calcium carbonate—in an amount in the range of about 9 to about 13 wt %, more preferably about 10 to about 12 wt %, and even more preferably about 11 wt % of the total solution weight; with water essentially comprising the remainder (in an amount ranging from about 55 to about 65 wt %, more preferably about 60 wt %.

With inclusion of the chalk in this embodiment as described, one may abate the tendency of the banded paper cigarettes to self-extinguish, enhance appearance of the product to an adult consumer and achieve these and other associated advantages.

The inclusion of an anti-wrinkling agent (preferably, such as propylene glycol) in an aqueous starch solution used to make banded wrapper in a manner consistent with the teaching herein can reduce transverse shrinkage to operationally manageable levels, alleviate pronounced wrinkling and essentially eliminate creasing problems that previously presented themselves. Inclusion of an anti-wrinkling agent has been found to have additional benefits, too. Cracking and flaking at bands are alleviated. In addition, the presence of the anti-wrinkling agent appears to cause the starch solution to reside more on the surface of the base web with less penetration into that material, and thus enhance film formation. Shrinkage of the wrapper in the vicinity of bands formed from an aqueous starch solution that includes an anti-wrinkling agent has been observed to be in the range of about 0.0625 to 0.125 in. for a 36 in. wide base web—a range which does not result in creasing nor excessive waviness in the base web. Furthermore, inclusion of an anti-wrinkling agent in the aqueous starch solution has been found to make possible the application of add-on material to be applied to the base web in a single application, printing pass, or the like, provided that sufficient drying capability is established with such practices. In addition, the pot life of the aqueous starch solution is materially improved by the inclusion of an anti-wrinkling agent as disclosed herein.

Cigarette Wrapper with Bands

Referring now to FIG. 2, the bands 126 of add-on material determine and regulate the IP and SE characteristics of the smoking article. Those bands 126 of add-on material are applied to a base web 140 (see FIG. 2) of the wrapper 123, which is then formed into a tobacco rod in conventional cigarette making equipment. Nominal permeability of the base web 140 may be in the range of about 20 to about 100 CORESTA. Currently, the preferred nominal permeability of the base web lies in the range of about 30 to about 70 CORESTA, with the most preferred nominal permeabilities being about 33 and about 60 CORESTA.

The manufacture of base web 140 preferably includes the production of a roll of base web of several feet across (usually about 3 feet across or in transverse dimension). The base web is then drawn through a printing press or the like and rewound to produce a roll of banded paper, which is then slit into bobbins.

It is further noted that the portion 133 of base web 140 outside of the bands 126 are preferably, essentially free of add-on material.

Preferably, each band 126 includes sufficient add-on material to reduce the diffusivity of the wrapper at each band to 0.0 to about 0.2 cm/sec, and more preferably to the range of 0.0 to about 0.1 cm/sec.

As presently understood, the banded regions of add-on material 126 according to this description permit a smoking article 120 (see FIG. 1) to be designed with an advantageous combination of low IP values and low SE values. The patterns of low permeability bands of add-on material provide areas of film-forming compound along the length of the tobacco rod 122 that can cooperate with a substrate to extinguish the lit smoking article 120 when it left smoldering and placed on the substrate, yet these regions of add-on material (such as a film-forming compound) cause the smoking article 120 to self-extinguish at statistically fewer occurrences when the smoking article 120 is held by an adult smoker in a free-burn condition. Thus, the smoking article 120 can exhibit a reduced ignition propensity while retaining a desirable free-burn quality or low SE value by applying a pattern of film-forming compound to the base web according to this description.

To achieve desirable IP and SE characteristics of the smoking article, a pattern 130 (see FIG. 9) is applied to the base web 140 of the wrapper paper, preferably while the base web 140 is in an unfolded condition or when the base web comprises a roll of cigarette paper that has yet to be slit into bobbins. An object of this description is to provide wrapper papers which, when formed into a tobacco rod 122, exhibit IP values no greater than 25 and SE values no greater than 50. Even more preferred, is an IP value for the resulting smoking article no greater than about 15; and the most preferred IP value for the resulting smoking article is no greater than about 10. Lower SE values are also desired. In this connection, a more preferred SE value is less than about 25; while the most preferred SE value is less than about 10.

The bands 126 of the pattern 130 may be formed by applying one or more layers of an aqueous film-forming composition to the base web of the wrapper paper to reduce the permeability of the paper in those bands. Alternatively, a cellulosic material may also be used to form the bands. Where a film-forming composition is used, that film-forming composition preferably may include water and a high concentration of an occluding agent, e.g., 20% to about 50% by weight. The film-forming compound can include one or more occluding agents such as starch, alginate, cellulose or gum and may also include calcium carbonate as a filler. Where starch is the film-forming compound, a concentration of about 21% may be advantageous. The film-forming composition may be applied to the base web of the wrapper paper 122′ using gravure printing, digital printing, coating or spraying using a template, or any other suitable technique. For example, the film-forming compounds and methods for applying film-forming compounds described in U.S. application Ser. No. 11/500,918, which is hereby incorporated herein in its entirety by this reference thereto, may be chosen for applying a pattern to the base web of the wrapper paper. If desired, the bands of add-on material can be formed by printing multiple, successive layers, e.g., two or more successive layers registered or aligned with one another. Furthermore, when layers are used to form the bands of add-on material, the material in layers may be the same of different. For example, one layer may be starch while the next layer may be starch and calcium carbonate (or vice versa).

Additionally, for a particular chosen pattern, the ability to extinguish the smoking article may depend more on providing minimum lengthwise extent of add-on material (e.g., a film-forming compound), rather than a particular weight per area of film-forming compound at longitudinal locations. The preferable length of a rectangular band or band, for example, may be no less than about 7 mm for a particular design, base web, and film-forming compound used. The amount of film-forming compound used may be increased to improve IP performance, usually without losing a free-burn quality, and if desired, a burn accelerator may be applied to the paper to support even higher add-on levels.

In that each row 131 of bands includes uncoated areas between bands 126, the smoking article has a significantly improved SE performance during free burn. The arrangement enables a smoking article to be designed with an SE value of less than 50% and significantly better. SE values at 0° may be much lower that the SE average value and may be less than 25%.

In the embodiments described above, the smoking article has a generally circular cross section. Therefore, it is possible for any side portion of the smoking article to rest against the substrate. However, a pattern as taught herein can be such that the burn characteristics described above (IP values no greater than 25% and SE values no greater than 50%) can be realized, regardless of which side portion of the smoking article happens to rest against the substrate.

The bands 126 of add-on material may be applied to the base web 140 preferably by a printing technique. While one or more printing technique (selected from the group consisting of direct printing, offset printing, inkjet printing, gravure printing, and the like) may be used to apply the band 126, preferably a gravure printing process will be used. Gravure printing provides ample control over deposition rates, deposition patterns, and the like, and is suitable for high-speed printing on the base web 140. For purposes of this disclosure, “high-speed” printing refers to printing processes where the base web 140 advances through the printing process at a linear speed greater than about 300 feet/min. For cigarette manufacturing purposes, base web printing speeds greater than 450 feet/min. are preferred, and speeds greater than 500 feet/minute or more are even more preferred. In this regard, the rates of deposition for add-on material, as well as the quality of the pattern of deposited add-on material, can vary considerably when wrapper prepared by high-speed printing processes is compared with wrapper prepared by low-speed printing processes. Higher-speed printing operations can achieve production of wrappers capable of providing both desirable IP values (performance) and desired SE values (performance).

Remarkably, it has been found that a base web may be converted (printed) to include bands in accordance with the embodiment described with reference to FIGS. 1 and 2 at about 1000 feet per minute with acceptable paper appearance (i.e., without quality defects) and without elevated or unacceptable statistical occurrences of creases or wrinkles.

This disclosure contemplates that various anti-wrinkling agents are suitable to attain the desired characteristics described herein. In particular, the anti-wrinkling agent is selected from the group consisting of glycerin, propylene glycol, and 1,2 propylene glycol. Propylene glycol is a preferred member of the anti-wrinkling agent group, however, 1,2 propylene glycol is the most preferred member of the anti-wrinkling agent group.

Bands 126 of this disclosure preferably comprise an aqueous solution containing starch, chalk or CaCO₃, and an anti-wrinkling agent. While many types of starch are contemplated, tapioca starch is presently preferred for the starch component of the layers of add-on material. A suitable commercially available starch is FLO-MAX8® available from National Starch & Chemical LLC (now Ingredion).

Many types of calcium carbonate particles are contemplated as falling within the spirit and scope of this disclosure. Presently, however, calcium carbonate available from Solvay Chemicals, Inc., as SOCAL 31 is a suitable commercially available calcium carbonate. SOCAL 31 is an ultrafine, precipitated form of calcium carbonate having an average particle size of about 70 nm (nanometers). Larger particles of calcium carbonate have been observed to not function as well in this application when compared to the ultrafine, precipitated form of calcium carbonate, due at least in part to the tendency of larger particles to precipitate from solution more quickly and due at least in part to the need for greater quantities to attain the beneficial characteristics discussed herein.

The film-forming compound can include one or more occluding agents such as starch, alginate, cellulose or gum and may also include calcium carbonate as a filler. Where starch is the film-forming compound, a concentration of about 21% may be advantageous. The film-forming composition may be applied to the base web of the wrapper 122′ using gravure printing, digital printing, coating or spraying using a template, or any other suitable technique.

Uncoated areas of the base web preferably do not comprise and are essentially free of any permeability reducing add-on material.

The manufacture of base web 140 usually will include the production of a roll of base web of several feet across (usually about 3 feet across or in transverse dimension). The base web is then drawn through a printing press or the like and rewound to produce a roll of banded paper, which is then slit into bobbins. Printing operations are preferably conducted on the rolls, but could be conducted after slitting. Preferably, the bobbins themselves will have a transverse dimension equivalent to the width needed to make tobacco rods 122 or an integral number of such widths (e.g., 1, 2, or 4 of such widths). The bobbins are adapted for use with typical cigarette making machinery. The wrapper preferably has a dimension in cross-direction that takes into account the nominal circumference of the tobacco rod and an overlapping seam. As a result, when the wrapper is slit, the smoking article formed therefrom always has a longitudinal seam with an exact overlap.

The base web advances or passes through a first gravure printing station where the first layer of each band is printed on the paper. The printing process may be applied to the “felt side” or the “wire side” of the base web, or both.

When an aqueous starch solution is being used as the add-on materials, its preparation for application before and at the printing press is preferably such that the add-on solution is maintained at or about 120° F. to about 140° F., as taught in commonly assigned U.S. patent application Ser. No. 13/324,747, filed Dec. 13, 2011.

Printing Apparatus

Referring now to FIG. 6, a preferred printing apparatus includes a dispensing reel 601, a collection reel 608, an engraved printing cylinder (gravure roller) 610, an impression cylinder 612, an optional backing roller 614, a nip 616 defined between the cylinder 610 and 612, a reservoir of add-on material 618, a pump 620 operative to pump add-on material from the reservoir 618, a heat exchanger 622, an applicator 624, a bath 626, a collector 627, a drain 628, a doctor blade 630, and an idler roller 634.

The impression cylinder 612 is mounted for counter-rotation on an axis parallel to the axis of the printing cylinder (or gravure roller) 610. In some applications, the impression cylinder includes a nonmetallic resilient surface. The impression cylinder is positioned between the roller and an optional backing roller 614, which is also mounted for rotation on an axis parallel to the axis of gravure the roller 610 and which counter-rotates relative to the impression cylinder. One of the functions provided by the optional backing roller 614 is stiffening the central portions of the impression cylinder so that the uniform printing pressure is obtained between the gravure roller 610 and the impression cylinder 612. The gravure roller 610 and the impression cylinder 612 cooperate to define a nip 616 through which the base web is drawn during the printing process. The nip 616 is sized to pinch the base web as it moves between the gravure cylinder 610 and the impression cylinder 612. The nip pressure 612 on the base web ensures the correct transfer of the add-on material from the gravure roller 610 to the paper base web 140.

In a preferred embodiment, the reservoir 628 contains the occlusive composition (add-on material), preferably an aqueous starch solution as discussed above for forming bands 126 on the base web 140. The reservoir communicates with a suitable pump 610 which is capable of handling the viscous occlusive composition. The occlusive composition may then flow to a suitable heat exchanger 622 where the temperature of the occlusive composition is elevated so that it lies in the range of about 40° to about 90° C. (about 120° F. to about 140° F.) so that the viscosity of the occlusive composition is adjusted to a level which is suitable for gravure printing and for maintain desired conditions of the starch solution. As discussed above, gravure printing usually requires a viscosity of less than about 200 cP. Preferably, the temperature of the occlusive composition is selected so that the viscosity is less than about 100 cP. For example, the occlusive composition may have a viscosity of about 10-40 cP at about 120° F.

While a separate heat exchanger 622 is disclosed, it may be desirable to provide thermal conditioning of the occlusive composition in the reservoir 618 itself. For example, heating elements and stirring apparatus may be included in the reservoir 618 to maintain the elevated temperature for the occlusive composition. Placement of the thermal conditioning in the reservoir has the advantage of making pump selection and operating requirements simpler since the pump need not handle the occlusive composition at the higher viscosity associated with lower temperatures because the occlusive composition would already be heated and, therefore, at the lower viscosity. Whether thermal conditioning occurs in the reservoir or in a separate heat exchanger, it is important that the thermal conditioning step occur at a controlled temperature selected to avoid scorching the occlusive composition. Scorching can cause discoloration of the occlusive composition, and can affect the occlusive characteristics of the composition.

Additionally, it is important to maintain an aqueous starch solution at or about the range of about 120° F. to 140° F. prior to and during printing operations. Aqueous starch solutions tend to degrade irreversibly if allowed to drop below those temperatures.

Regardless of where the thermal conditioning step occurs, the heated occlusive composition is preferably delivered to a suitable applicator 624 that spreads the occlusive composition across the width of the gravure cylinder. That spreading step may be effected by pouring or spraying the occlusive composition onto the gravure cylinder, or by delivering the liquid occlusive composition to a collector 627 to establish a bath 626 of occlusive composition in contact with a lower portion of the gravure cylinder 610. The gravure cylinder 610 may be heated to prevent premature cooling of the composition.

Generally, the collector 627 extends partially about the gravure roller to a height sufficient to collect the bath, but to a height well below the top of the gravure cylinder 610. When the bath reaches the top of the collector, occlusive composition can flow through a drain 628 at the bottom of the apparatus back into the reservoir. Thus, the occlusive composition circulates through the printing station and can be maintained at suitable printing viscosity by the thermal conditioning apparatus discussed above.

Printing Cylinder

Referring now to FIG. 7, the preferred embodiment includes an engraved printing cylinder (print roller) 610 having a plurality of engraved regions 611, 611′ in spaced-apart relation about the circumference of the cylinder 610 corresponding to the desired width “w” of the bands and the desired spacing “s” between bands or rows as indicated by arrows “w” and “s” respectively, in FIG. 1. Each engraved region 611, 611′ correspond with a row 131, 131′ in FIG. 9 Preferably the engraved regions 611 are each slightly angulated in the form of a chevron. The angle “A” at the tip 901 of the chevron is greater than about 170 degrees. Such arrangement helps to further relieve stress in the paper base web 140 upon application of the add-on material, by spreading any puckering or wrinkling in opposing directions on the left and right halves of the web along the machine direction. It is envisioned that the engraved regions 611 might be instead arranged linearly without any chevron.

Preferably, the circumference of the roller is determined such that it is an integer multiple of the sum of the nominal distance between bands plus the band width. Thus, for each revolution of the roller, that predetermined integer number of bands is printed on the base web 123.

Printing consistency and efficiency is further enhanced by elevating nip-pressure at the press. In a preferred embodiment, a nip pressure was increased by approximately 10 to 15%, e.g., from the normally applied pressure of about 45-65 psi to about 60-70 psi. To further enhance printing consistency, clarity and uniformity, the core of the impression roller should be strengthened by a selection of material and/or increase in diameter by 100 to 150% from that typically installed. With such arrangement “crowning” at the center of the impression roller is abated.

In the preferred embodiment, as shown in FIG. 8, each web 140 is printed with multiple bands 131 a-131 d along the length thereof. Preferably, the bands 131 a-d are printed in a chevron pattern on the base web (prior to slitting) such that the apex 700 in the leading edge of each band 126 is essentially transversely disposed of the outer points 710, 710′ on the trailing edge 148 of the preceding band 126. In other words, the apex 700 and the outer points 710, 710′ essentially lie along an imaginary transverse line 702. It is envisioned that the angle at the apex 700 may be adjusted to re-establish the aforementioned relationship if the roll width is increased or decreased. In the alternative, the apex 700 may be established slightly ahead in a machine direction of outer points 710, 710′ of an adjacent band 126.

The etched regions 611, 611′ of the gravure roller 610 (FIG. 7) are configured and mutually arranged correspondingly. This chevron shape and relationship helps avoid excessive waviness in the web as a result of printing operations so that rewinding the printed web and the slitting the web into bobbins may be conducted without unacceptable occurrences of creases and tears. More particularly, it is to be noted that along any transverse region (or imaginary line) across the entire base web 140 after application of the add-on composition, the transverse region will include portions of the base web 140 that are not treated with add-on material as well as portions that are treated with add-on material. In contrast, without the chevrons (i.e., the bands are arranged straight across the web), the shrinking effect of the aqueous add-on material during drying is localized at the location of the bands such that some transverse regions of the web is subject to all the shrinking effect and some adjacent transverse regions are not, which circumstance is known to exacerbate waviness, which in turn leads to creasing and tears in the web during rewinding and slitting.

With the chevrons (FIG. 8) the shrinking effect of the add-on composition is distributed with a longitudinal component and no longer does any thin, imaginary transverse region bear the entirety of an application of add-on material. Consequently, tendencies for creasing and tearing are abated. Accordingly, when the add-on material is dried, the related transverse web shrinkage is not localized in the printed (i.e., band) areas, rather that shrinkage rate gradually increases from a minimum value at the leading at the apex 700 to the trailing edge apex 709 at the apex, and remains substantially constant until the leading edge 126 of the band (the respective row 131) reaches the lateral edge of the band. From that location, the shrinkage decreases until the trailing edge of the band where the minimum shrinkage value exists. Thus, rather than step-wise shrinkage discontinuity, the chevron printing design gives gradual shrinkage variation and results in reduced waviness compared to prior techniques which used parallel bands disposed perpendicularly across the base web.

Still referring to FIG. 8, once the base web 140 has been printed with the chevron shaped rows 131 of bands 126, the base web is rolled and then slit longitudinally into a plurality of parallel ribbons that are wound into bobbins. Typically the base web may have a transverse width of about 50 inches, while individual ribbons may have a transverse width of about 26 to 28 mm or multiples thereof with a length of material on the order of 6,000 feet. Accordingly, the base web 140 of about 50 inch width generates about 45 to about 50 ribbons or bobbins. Each individual ribbon is collected by tightly winding it on a corresponding bobbin, where each bobbin may have a length of material on the order of 6,000 feet. The bobbins may then be used in conventional cigarette making machinery in combination with tobacco material to form a tobacco rod. The tobacco rods are then severed at predetermined lengths, such that filters can be attached with tipping paper to form finished cigarettes or smoking articles.

EXAMPLES

In a first example, bobbins of 33 CORESTA banded wrapper were constructed in accordance with the form and dimensions of the first described embodiment (see FIG. 3). The add-on solution comprised water, starch, calcium carbonate and 1,2 propylene glycol as taught herein. The add-on material was applied in a single pass gravure printing operation utilizing chevron and solution preparation and thermal maintenance as taught herein. The target diffusivity was zero at the bands. Cigarettes were constructed with the wrappers and tested for IP and SE performance, with the results of an overall IP of 10.8% and an overall, average SE value of 46.4%. Such is a significant and surprisingly low SE value coupled with acceptable IP performance.

In a second example, bobbins of 33 CORESTA banded wrapper were constructed in accordance with the form and dimensions of the second described embodiment (see FIG. 4). The add-on solution comprised water, starch, calcium carbonate and 1,2 propylene glycol as taught herein. The add-on material was applied in a single pass gravure printing operation utilizing chevron and solution preparation and thermal maintenance as taught herein. The target diffusivity was zero at the bands. Cigarettes were constructed with the wrappers and tested for IP and SE performance, with the results of an overall IP of 6.0% and an overall, average SE value of 69.4%. Such is a significant and surprisingly low SE value coupled with acceptable IP performance.

It will now be apparent to those skilled in the art that this specification describes a new, useful, and nonobvious smoking article. It will also be apparent to those skilled in the art that numerous modifications, variations, substitutes, and equivalents exist for various aspects of the smoking article that have been described in the detailed description above. Accordingly, it is expressly intended that all such modifications, variations, substitutions, and equivalents that fall within the spirit and scope of the invention, as defined by the appended claims, be embraced thereby. 

We claim:
 1. A method of achieving ignition propensity performance in a smoking article together with statistically fewer self-extinguishments in such smoking articles, comprising: establishing on a wrapper of said smoking article a plurality of crenellated bands arranged in circumferential extending, longitudinally spaced-apart relation; said establishing step including establishing said bands at predetermined size and diffusivity value such that said smoking article exhibits an IP performance of less than about 15%; and exhibits an average SE performance less than about 50%.
 2. The method of claim 1, wherein said diffusivity value is established in the range of 0 to about 0.2 cm/sec.
 3. The method of claim 2, further including establishing the bands by single-pass printing an aqueous solution containing starch, calcium carbonate, and an anti-wrinkling agent.
 4. The method of claim 3, said establishing further comprises applying the rows of bands to a base web according to a chevron form.
 5. A process of making wrapper for a smoking article comprising: applying an add-on material on a base web in the form of a plurality of crenellated bands; and controlling diffusivity values in the bands to lie in the range of 0 to about 0.2 cm/sec using an aqueous solution of starch, calcium carbonate, and an anti-wrinkling agent.
 6. The process of claim 5, further including selecting the anti-wrinkling agent from the group consisting of propylene glycol; 1,2 propylene glycol; and glycerin.
 7. The process of claim 4, further including slitting the base web to form bobbins.
 8. The process of claim 4, wherein the bands are applied to the base web in a chevron pattern.
 9. The process of claim 8, wherein the zones of bands are applied to the base web in a chevron pattern such that an apex of a lagging chevron is essentially transverse of an outer edge portion of a leading chevron.
 10. The process of claim 9, wherein the chevron pattern has an angle with respect to the transverse direction of the web, which angle lies in the range of about 0.5° to about 5°. 